Ask, task, task, cask, flask, mask, hask.†
ASM.
Chasm, spasm, miasm, enthusiasm, cataplasm, phantasm.
ASP.
Asp, clasp, rasp, gasp, grasp, hasp, wasp (?).
ASQUE.
Casque, mask, etc.
ASS.
Ass, brass, class, grass, lass, mass, pass, alas, amass, cuirass, repass, surpass, morass, etc.
AST.